Characterizing Engine Load

ABSTRACT

Aspects of the disclosure are directed to characterizing effective vehicle frontal area. As may be implemented in accordance with one or more embodiments, one or more operating parameters of the vehicle are obtained. Such parameters may be obtained during one or more qualifying periods of time, such as those periods in which an operating parameter or parameters such as speed and/or acceleration are within a range of values. A value that provides an estimate of the vehicle frontal area is then generated based on the one or more operating parameters.

FIELD OF THE INVENTION

This invention relates to an apparatus and method for characterizingvehicle structure, such as by characterizing frontal area and/or otheraspects affecting drag or other aerodynamic properties.

In particular, the invention relates to measurement of fuel consumption,of vehicles. We will describe an apparatus and method for means forestimating fuel consumption and/or emissions, for land vehicles,including an apparatus and method for dynamically providing an accurateestimate of fuel consumption, and/or emissions, of a particular vehicleand driver, during the course of a journey, dependent on a combinationof characteristics of the particular land vehicle, driver behaviour, andjourney as the journey progresses.

BACKGROUND

In our earlier patents and patent applications we described devices andmethods for determining fuel consumption and/or emissions for landvehicles (“vehicles”) using signals obtained from the vehicle's enginemanagement system through the on-board diagnostics port (OBD, OBDII, CANand similar herein referred to as the ‘OBD port’). Often the requireddata is not available, or not available in a readily usable form, fromthe OBD port, and in our patent application (PCT no. WO2008/146020) wedescribe how other signals from the engine management system can beidentified and used to determine fuel consumption and/or emissionsvalues. Such information can also be used to infer driver behaviourwhich can be used for driver monitoring or training.

In some instances, not only some information required to perform thefuel/emissions calculations may not be available, but can even beblocked by the vehicle manufacturer. In these instances another approachis required.

There are many occasions, and many persons and entities, who would findit useful to have access to accurate predictions of fuel consumption ofa vehicle on an instant to instant basis during the course of a journey.Such predictions would need to reflect the characteristics of theparticular vehicle being driven and the behaviour of the driver duringthe course of the journey, and these characteristics would be influencedby the characteristics of the journey.

Attempts have been made to provide estimates of fuel consumption andemissions but tend to be based on averages and generalities rather thanspecifics of each vehicle, driver and journey, utilised on an instant toinstant basis.

It would be helpful to have accurate values for fuel consumption duringthe course of a journey dependent on characteristics of the vehicle,driver behaviour, and journey, for example for fleet owners, haulage andlike companies, and insurance companies, among others, to best managetheir business.

The present invention seeks to provide such accurate values.

SUMMARY OF THE INVENTION

According to a first aspect, the present invention comprises a method ofestimating the fuel consumption of a vehicle said method comprising thesteps of estimating an overall power of said vehicle, by estimating arolling power component, an aerodynamic resistance component and anacceleration component, using at least one parameter obtained from an onboard diagnostic system of the vehicle; determining the type of fuelused by the vehicle; and estimating said fuel consumption by summingsaid components of said overall power and dividing by the energy valueof said fuel type and by a predetermined engine efficiency value.

Preferably, the rolling power component is estimated using an estimatedvalue of mass of the vehicle and/or the aerodynamic resistance isestimated using an estimated value of the frontal area of the vehicle.Preferably, the steps of estimating said vehicle mass or said frontalarea comprises the step of identifying qualifying periods in which atleast one motion parameter is within a predetermined range of valuesassociated with that parameter. Preferably, the step of estimating saidvehicle mass comprises the step of determining a weighted or movingaverage value of vehicle acceleration readings taken during qualifyingperiods and/or the step of determining a weighted or moving averagevalue of overall power readings taken during qualifying periods.

Preferably, one of said motion parameters for identifying saidqualifying period for estimating vehicle mass consists of said vehicleacceleration and/or one of said motion parameters for identifying saidqualifying period for estimating frontal area consists of said vehicleacceleration. Preferably, the criterion for identifying said qualifyingperiod is that said vehicle acceleration is above a predeterminedthreshold, said threshold being chosen to identify near peakacceleration and/or is between predetermined thresholds, said thresholdsbeing chosen to identify periods of near steady state motion. Preferablythe method further comprises the step of identifying an engine loadreporting strategy for said vehicle, using at least one OBD parameter.

Preferably, the step of identifying said engine load reporting strategycomprises the steps of obtaining said engine load and said engine speedand comparing said engine load with an engine load threshold associatedwith said engine speed. Preferably, the engine load threshold is chosento identify periods in which said engine is idling. Preferably, a forceprovided to cranks of said vehicle is estimated using an empiricallyderived relationship between force and engine size.

Preferably, the method further comprises a method for discovering whichof a plurality of possible engine load reporting strategies is used byan On-board Diagnostics system in a vehicle with an engine, comprisingexamining On-board Diagnostics system parameters, and determining theengine load when the engine is operating in such a manner as tosubstantially maximise the difference between the engine load valueswhich would be produced by the different engine load reportingstrategies.

Preferably, the method further comprises identifying periods in whichsaid engine is idling as to substantially maximise the differencebetween the engine load values which would be produced by the differentengine load reporting strategies.

Preferably, periods in which said engine is idling are identified byusing said On-board Diagnostics system parameters and/or by comparingsaid engine speed with an idling speed threshold.

Preferably, the method further comprises of adjusting said idlingthreshold speed to allow for a time for which said engine has beenrunning and/or to allow for an engine temperature and/or to allow for anengine capacity and/or to allow for a fuel type of said engine.

Preferably, the method further comprises said step of performing a checkto discover whether said vehicle is being held in a stationary state bymeans of engaging a clutch plate. Preferably, said check is performed bycomparison of a reported engine load with an engine load threshold.Preferably, the method further comprises performing a check that saidengine is running. Preferably, the method further comprises performing apersistency check on said discovered reporting strategy.

Preferably, the method further comprises using of a latch circuit tostore an indicator as to said discovered reporting strategy.

Preferably, a speed of said vehicle is used in discovering saidreporting strategy.

Preferably the method further comprises a method of estimating aneffective frontal area or aerodynamic resistance of a vehicle includingan engine comprising; at a substantially constant speed of the vehicledetermining the total power of the engine and determining the rollingresistance power to overcome the rolling resistance of the vehicle atthat substantially constant speed; subtracting the determined rollingresistance power from the determined total current power to determinethe aerodynamic resistance of the vehicle or the effective frontal area.

Preferably, the method further comprises identifying periods in whichsaid vehicle is travelling at a substantially constant speed.Preferably, the step of identifying said periods of substantiallyconstant speed comprises use of on board diagnostic system output and/oruse of one or more of a vehicle speed, a vehicle acceleration, an enginespeed and an engine load and/or comparing one or more of vehicle speed,vehicle acceleration, engine speed and engine load with predeterminedreference levels.

Preferably, the method further comprises the step of estimating saidtotal current power for said vehicle during a period in which saidvehicle travelling at a substantially constant speed. Preferably, thestep of estimating said total current power comprises use of an engineload parameter provided by said On Board Diagnostic system. Preferably,the method further comprises the step of adjusting said total currentpower by allowing for transmission losses. Preferably, the step ofadjusting said total current power to allow for transmission lossescomprises the step of subtraction and/or multiplication of said totalcurrent power by one or more empirical power factors. Preferably, themethod further comprises the step of finding a moving or weightedaverage for said total current power over a plurality of periods ofsubstantially constant speed.

Preferably, the method further comprises the step of estimating saidaerodynamic resistance power by estimating rolling resistance power andsubtracting said rolling resistance power from said total current power.

Preferably, the step of estimating rolling resistance comprises usingestimates of said vehicle's mass, said coefficient of drag and saidvehicle speed. Preferably, the step of estimating rolling resistancefurther comprises making allowance in said estimation of rollingresistance for a gradient on which said vehicle may be travelling.

Preferably, the method further comprises a method for determining thefuel type of a vehicle, comprising obtaining the output parameters of anOn Board Diagnostic (OBD) system of the vehicle, and using said outputparameters to determine the fuel type used by the vehicle.

Preferably, the method comprises identifying whether the engine is beingthrottled, or measuring whether the exhaust gases are in the rangetypical of a diesel engine or a petrol engine, or checking the fuelpressure, or using a plurality of fuel type identifying methods andfurther comprising assigning a weighting to the output of each of theplurality of fuel type identifying methods, said weighting varyingaccording to the type of fuel identifying method and summing theweightings and compare the sum of the weightings to a predeterminedthreshold, to decide the fuel type of the vehicle.

Preferably, the method comprises the step of identifying whether theengine is being throttled comprises comparing the Manifold AbsolutePressure (MAP) with a threshold and/or comparing the air flow with apredetermined proportion of the engine capacity.

Preferably, the method comprises the step of checking whether theexhaust gases are in the range typical of a diesel engine or a petrolengine and/or checking the OBD protocol and/or checking the fuel statusparameter identifier of an OBD system.

Preferably, the method comprises the step of allowing a manual overrideof the results of the automatic detection of fuel type.

Preferably, the method further comprises a method of estimating the massof a vehicle; said vehicle having motion parameters comprising a vehiclespeed parameter, a vehicle acceleration parameter and a maximumacceleration parameter, said vehicle having an engine, said enginehaving an engine capacity parameter and engine activity parameterscomprising an engine speed parameter, a power parameter, a maximum powerparameter and an engine load parameter, said method comprising the stepof determining a weighted or moving average value of vehicleacceleration parameters taken during qualifying periods wherein at leastone of the motion parameters and/or at least one of the engine activityparameters are within a predetermined range and using said weighted ormoving average value of vehicle acceleration to estimate the mass of thevehicle.

Preferably, the value of at least one of said at least one motionparameters or engine activity parameters is obtained from at least oneoutput parameter of an on board diagnostic system.

Preferably, the method further comprises the step of identifying nearpeak acceleration periods in which at least one of the at least onemotion parameters or engine activity parameters indicates that the saidvehicle is accelerating at near to its maximum acceleration.

Preferably, said at least one output parameter is one of the engineload, engine speed, vehicle speed and vehicle acceleration.

Preferably, the method further comprises the step of comparing saidvehicle acceleration with at least one predetermined accelerationthreshold and/or comparing said vehicle speed with a first predeterminedvehicle speed threshold and/or comparing said vehicle speed with asecond predetermined vehicle speed threshold and/comparing said engineload with at least one predetermined engine load threshold and/orcomparing said engine speed with at least one predetermined engine speedthreshold.

Preferably, each of the at least one predetermined thresholds isassigned a value according to the type of vehicle.

Preferably, said weighted or moving averaging is performed only if atleast one of said motion parameters or engine activity parameters iswithin a predetermined range or only if a plurality of said motionparameters or engine activity parameters is within a predetermined rangeset for the said parameter or only if all of said motion parameters orengine activity parameters is within a predetermined range set for saidparameter.

Preferably, the method further comprises determining a force provided toa crank of the vehicle during qualifying periods. Preferably, the methodfurther comprises the step of estimating said mass of said vehicle bydividing said force by said weighted or moving average accelerationvalue. Preferably, the method further comprises the step of checkingwhether at least one qualifying period has occurred.

Preferably, the method further comprises the step of estimating a valueof said force provided to said crank using said engine size andempirically determined constants. Preferably, said value of said forceis used in the calculation of mass if no qualifying period has occurred.

Preferably, the method further comprises the steps of obtaining orestimating an air flow through said engine; calculating a provisionalfuel mass estimate by dividing the obtained or estimated air flow by astoichiometric ratio associated with the fuel type; estimating the fuelconsumption by dividing said provisional fuel mass estimate by an oxygencontent parameter derived from an analysis of exhaust gases. Preferably,the method comprises measuring a mass air flow and/or estimating saidair flow using the ideal gas equation, using estimates of pressure,volume flow rate and temperature.

Preferably, the method comprises estimating said pressure using aManifold Absolute pressure sensor and/or using a Manifold Airtemperature sensor.

Preferably, the method comprises calculating said estimate of saidvolume flow rate using an engine size and an engine speed.

Preferably, the method comprises obtaining said oxygen content parameterfrom an exhaust oxygen sensor or from a look-up table, said tableproviding oxygen content values according to engine speed and vehicletype.

Preferably, the method further comprises estimating an overall power ofsaid vehicle by estimating a rolling power component, an aerodynamicresistance component and an acceleration component, using at least oneparameter obtained from an on board diagnostic system of the vehicle;determining the type of fuel; and estimating said fuel consumption bysumming said components of said overall power and dividing by the energyvalue of said fuel type and by a predetermined engine efficiency value.

Preferably, the method further comprises estimating an upper limit andlower limit for vehicle mass. Preferably, the method further comprisesestimating an upper limit and a lower limit for fuel consumption, basedon said upper limit of mass and said lower limit of mass respectively.

According to a second aspect, the present invention comprises apparatusfor estimating the fuel consumption of a vehicle, said apparatuscomprising estimating means for estimating and providing a parameterrelating to overall power of the vehicle estimating means for estimatingand providing a parameter relating to a rolling power component,estimating means for estimating and providing a parameter relating anaerodynamic resistance component and estimating means for estimating andproviding a parameter relating to acceleration component, said overallpower estimating means being adapted to be connected to an on boarddiagnostic system of the vehicle to receive and use at least oneparameter obtained therefrom; means to provide a parameter indicatingthe type of fuel used; and means connected to receive the parametersrelating to the estimated rolling power component, the estimatedaerodynamic resistance component and the estimated accelerationcomponent and to estimate said fuel consumption by summing saidcomponents of said overall power and dividing by the energy value ofsaid fuel type and by a predetermined engine efficiency value.

Preferably, the means for estimating the rolling power component uses anestimated value of mass of the vehicle.

Preferably, the means for estimating the aerodynamic resistance uses anestimated value of the frontal area of the vehicle.

Preferably, means for estimating said vehicle mass or said frontal areais adapted to identify qualifying periods in which at least one motionparameter is within a predetermined range of values associated with thatparameter.

Preferably, means for estimating said vehicle mass is adapted todetermine a weighted or moving average value of vehicle accelerationreadings taken during qualifying periods.

Preferably, the method further comprises to determine one of said motionparameters for identifying said qualifying period for estimating vehiclemass and wherein said parameter consists of said vehicle acceleration.

Preferably, the apparatus is adapted to identify a qualifying period inwhich said vehicle acceleration is above a predetermined threshold, saidthreshold being chosen to identify near peak acceleration. Preferably,means for estimating said frontal area is adapted to determine aweighted or moving average value of overall power readings taken duringqualifying periods.

Preferably, the apparatus is adapted to receive one of said motionparameters for identifying said qualifying period for estimating frontalarea and where said parameter consists of said vehicle acceleration.

Preferably the apparatus is adapted to identify a qualifying period inwhich said vehicle acceleration is between predetermined thresholds,said thresholds being chosen to identify periods of near steady statemotion.

Preferably, the apparatus further comprises means for identifying anengine load reporting strategy for said vehicle, using at least one OBDparameter.

Preferably, said means for identifying said engine load reportingstrategy is adapted to obtain said engine load and said engine speed andto further compare said engine load with an engine load thresholdassociated with said engine speed.

Preferably, the apparatus is adapted to estimate a force provided tosaid crank using an empirically derived relationship between force andengine size.

Preferably, the apparatus further comprises apparatus for discoveringwhich of a plurality of possible engine load reporting strategies isused by an On-board Diagnostics system in a vehicle with an engine,comprising examining means to examine On-board Diagnostics systemparameters, and means to determine the engine load when the engine isoperating in such a manner as to substantially maximise the differencebetween the engine load values which would be produced by the differentengine load reporting strategies.

Preferably, the apparatus further comprises identifying means toidentify periods in which said engine is idling as to substantiallymaximise the difference between the engine load values which would beproduced by the different engine load reporting strategies.

Preferably, said identifying means identifies periods in which saidengine is idling by using said On-board Diagnostics system parametersand/or by comparing said engine speed with an idling speed threshold.

Preferably, the apparatus further comprises means to adjust said idlingthreshold speed to allow for a time for which said engine has beenrunning.

Preferably, the apparatus is adapted to adjust said idling thresholdspeed to allow for an engine temperature and/or to allow for an enginecapacity and/or to allow for a fuel type of said engine and/or to allowfor an engine capacity.

Preferably, the apparatus further comprises a clutch checking means todiscover whether said vehicle is being held in a stationary state bymeans of engaging a clutch plate.

Preferably, said clutch checking means compares a reported engine loadwith an engine load threshold. Preferably, the apparatus furthercomprises engine checking means to check that said engine is running.

Preferably, the apparatus further comprises persistency check means toperform a persistency check on said discovered reporting strategy.

Preferably, the apparatus further comprises a latch circuit to store anindicator as to said discovered reporting strategy.

Preferably, the apparatus further comprises speed checking means whereina speed of said vehicle is used in discovering said reporting strategy.

Preferably, said speed of said vehicle is used to identify periods inwhich said vehicle is idling.

Preferably, the apparatus further comprises apparatus for estimating aneffective frontal area or aerodynamic resistance of a vehicle includingan engine comprising; apparatus for determining the total power of theengine at a substantially constant speed of the vehicle and apparatusfor determining the rolling resistance power to overcome the rollingresistance of the vehicle at that substantially constant speed;apparatus for subtracting the determined rolling resistance power fromthe determined total current power to determine the aerodynamicresistance of the vehicle or the effective frontal area.

Preferably, the apparatus further comprises identifying means adapted toidentify periods in which said vehicle is travelling at a substantiallyconstant speed. Preferably, said identifying means is adapted toidentify periods of substantially constant speed using on boarddiagnostic system output and/or using one or more of said vehicle speed,said vehicle acceleration, said engine speed and said engine load.

Preferably, the apparatus further comprises estimating means adapted toprovide an estimate of said total current power for said vehicle duringa period of travelling at a substantially constant speed and/or by usingan engine load parameter provided by said OBD system.

Preferably, said adjusting means is adapted to adjust current power toallow for transmission losses by subtraction and/or multiplication ofsaid total current power by one or more empirical power factors.Preferably, the apparatus further comprises averaging means adapted tofind a moving or weighted average for said total current power over aplurality of periods of substantially constant speed.

Preferably, said identifying means is adapted to identify periods ofsubstantially constant speed by comparing one or more of vehicle speed,vehicle acceleration, engine speed and engine load with predeterminedreference levels.

Preferably, the apparatus further comprises aerodynamic resistanceestimating means to estimate said aerodynamic resistance power byestimating rolling resistance power and subtracting said rollingresistance power from the total current power.

Preferably, said rolling resistance estimating means estimates saidrolling resistance by using estimates of said vehicle's mass, saidcoefficient of drag and said vehicle speed.

Preferably, said rolling resistance estimating means makes allowance insaid calculation of rolling resistance for a gradient on which saidvehicle may be travelling.

Preferably, the apparatus further comprises apparatus for determiningthe fuel type of a vehicle, comprising means to obtain the outputparameters of an On Board Diagnostic (OBD) system of the vehicle, andmeans to use said output parameters to determine the fuel type used bythe vehicle.

Preferably, the apparatus comprises a throttling identifying means toidentify whether the engine is being throttled.

Preferably, the apparatus comprises pressure comparison means adapted tocompare the Manifold Absolute Pressure (MAP) with a predeterminedthreshold and/or air flow comparison means adapted to determine whetherthe air flow is less than a predetermined proportion of the enginecapacity and/or an exhaust gas temperature comparison means to measurewhether the exhaust gases are in the range typical of a diesel engine ora petrol engine and/or a protocol checking means to check the OBDprotocol and/or a fuel status checking means to check the fuel statusparameter identifier of an OBD system and/or a manual override to allowa user to override the results of the automatic detection of fuel type.

Preferably, the apparatus further comprises a throttle identifying meansto identify whether the engine is being throttled, or an exhaust gastemperature comparison means to measure whether the exhaust gases are inthe range typical of a diesel engine or a petrol engine, or a fuelpressure checking means to check the fuel pressure, or a plurality offuel type identifying means and further comprising weighting means toassign a weighting to the output of each of the plurality of fuel typeidentifying means, said weighting varying according to the type of fuelidentifying means and the output of the fuel identifying, and a decisionmeans to sum the weightings and compare the sum of the weightings to apredetermined threshold, enabling a decision as to the fuel type of thevehicle.

Preferably, the apparatus further comprises apparatus for estimating themass of a vehicle having an engine, said apparatus comprising; means todetermine motion parameters of the vehicle comprising a vehicle speedparameter, a vehicle acceleration parameter and a maximum accelerationparameter, means to determine an engine capacity parameter and engineactivity parameters comprising an engine speed parameter, a powerparameter, a maximum power parameter and an engine load parameter, meansto determine a weighted or moving average value of vehicle accelerationparameters taken during qualifying periods wherein at least one of themotion parameters and/or at least one of the engine activity parametersare within a predetermined range and means for using said weighted ormoving average value of vehicle acceleration to estimate the mass of thevehicle.

Preferably, the apparatus is adapted to obtain the value of at least oneof said at least one motion parameters or engine activity parameters isobtained from at least one output parameter of an on board diagnosticsystem.

Preferably, the apparatus is adapted to identify near peak accelerationperiods in which at least one of said at least one motion parameters orengine activity parameters indicates that the said vehicle isaccelerating at near to its maximum acceleration.

Preferably, said at least one output parameter is one of the engineload, engine speed, vehicle speed and vehicle acceleration.

Preferably, the apparatus further comprises comparison means to comparesaid vehicle acceleration with at least one predetermined accelerationthreshold. Preferably, the apparatus further comprises comparison meansadapted to compare said vehicle speed with a first predetermined vehiclespeed threshold.

Preferably, the apparatus further comprises comparison means to comparesaid vehicle speed with a second predetermined vehicle speed thresholdand/or to compare said engine load with at least one predeterminedengine load threshold and/or to compare said engine speed with at leastone predetermined engine speed threshold. Preferably, each of said atleast one predetermined thresholds is assigned a value according to thetype of vehicle.

Preferably, the apparatus is adapted such that said weighted or movingaveraging is performed only if at least one of said motion parameters,or engine parameters is within a predetermined range for said parameteror only if a plurality of said motion parameters or engine parameters iswithin a predetermined range set for the said parameter or only if allof said motion parameters is within a predetermined range set for saidparameter.

Preferably, the apparatus further comprises force determining means todetermine a force provided to said crank during qualifying periods.

Preferably, the apparatus further comprises estimating means to estimatesaid mass of said vehicle by dividing said force by said weighted ormoving average acceleration value.

Preferably, the apparatus further comprises checking means to checkwhether at least one qualifying period has occurred.

Preferably, the apparatus further comprises estimating means to estimatea value of said force provided to said crank using said engine size andempirically determined constants.

Preferably, the apparatus is adapted to use said value of said force inthe calculation of mass if no qualifying period has occurred.

Preferably, the apparatus further comprises apparatus for estimating thefuel consumption of an engine in a vehicle comprising means forobtaining or estimating an air flow through said engine; means forcalculating a provisional fuel mass estimate by dividing the obtained orestimated air flow by a stoichiometric ratio associated with the fueltype; means for estimating the fuel consumption by dividing saidprovisional fuel mass estimate by an oxygen content parameter derivedfrom an analysis of exhaust gases.

Preferably, said determining means further comprises measuring meansusing a mass air flow sensor, and estimating means to estimate said airflow using the ideal gas equation, using estimates of pressure, volumeflow rate and temperature.

Preferably, the apparatus is adapted to obtain said pressure estimateusing a Manifold Absolute pressure sensor and/or using a Manifold Airtemperature sensor.

Preferably, the apparatus is adapted to calculate said estimate of saidvolume flow rate using an engine size and an engine speed.

Preferably, the apparatus is adapted to obtain said oxygen contentparameter from an exhaust oxygen sensor or from a look-up table, saidtable providing oxygen content values according to engine speed andvehicle type.

Preferably, the apparatus further comprises estimating means to estimatean overall power of said vehicle, by estimating a rolling powercomponent, an aerodynamic resistance component and an accelerationcomponent, using at least one parameter obtained from an on boarddiagnostic system of the vehicle; determining the type of fuel; andestimating said fuel consumption by summing said components of saidoverall power and dividing by the energy value of said fuel type and bya predetermined engine efficiency value.

Preferably, the apparatus further comprises estimating means to estimatean upper limit and lower limit for vehicle mass.

Preferably, the apparatus further comprises estimating means to estimatean upper limit and a lower limit for fuel consumption, based on saidupper limit of mass and said lower limit of mass respectively.

According to a further aspect, the present invention provides anapparatus for discovering which of a plurality of possible engine loadreporting strategies is used by an On-board Diagnostics system in avehicle with an engine, comprising examining means to examine On-boardDiagnostics system parameters, and means to determine the engine loadwhen the engine is operating in such a manner as to substantiallymaximise the difference between the engine load values which would beproduced by the different engine load reporting strategies.

According to a further aspect, the present invention provides a methodfor discovering which of a plurality of possible engine load reportingstrategies is used by an On-board Diagnostics system in a vehicle withan engine, comprising examining On-board Diagnostics system parameters,and determining the engine load when the engine is operating in such amanner as to substantially maximise the difference between the engineload values which would be produced by the different engine loadreporting strategies.

According to a further aspect, the present invention provides a methodof estimating an effective frontal area or aerodynamic resistance of avehicle including an engine comprising; at a substantially constantspeed of the vehicle determining the total power of the engine anddetermining the rolling resistance power to overcome the rollingresistance of the vehicle at that substantially constant speed;subtracting the determined rolling resistance power from the determinedtotal current power to determine the aerodynamic resistance of thevehicle or the effective frontal area.

According to a further aspect, the present invention provides apparatusfor estimating an effective frontal area or aerodynamic resistance of avehicle including an engine comprising; apparatus for determining thetotal power of the engine at a substantially constant speed of thevehicle and apparatus for determining the rolling resistance power toovercome the rolling resistance of the vehicle at that substantiallyconstant speed; apparatus for subtracting the determined rollingresistance power from the determined total current power to determinethe aerodynamic resistance of the vehicle or the effective frontal area.

According to a further aspect, the present invention provides anapparatus for determining the fuel type of a vehicle, comprising meansto obtain the output parameters of an On Board Diagnostic (OBD) systemof the vehicle, and means to use said output parameters to determine thefuel type used by the vehicle.

Preferably, the apparatus comprises a throttle identifying means toidentify whether the engine is being throttled, or an exhaust gastemperature comparison means to measure whether the exhaust gases are inthe range typical of a diesel engine or a petrol engine, or a fuelpressure checking means to check the fuel pressure, or a plurality offuel type identifying means and further comprising weighting means toassign a weighting to the output of each of the plurality of fuel typeidentifying means, said weighting varying according to the type of fuelidentifying means and the output of the fuel identifying, and a decisionmeans to sum the weightings and compare the sum of the weightings to apredetermined threshold, enabling a decision as to the fuel type of thevehicle.

According to a further aspect, the present invention provides a methodfor determining the fuel type of a vehicle, comprising obtaining theoutput parameters of an On Board Diagnostic (OBD) system of the vehicle,and using said output parameters to determine the fuel type used by thevehicle.

Preferably, the method comprises identifying whether the engine is beingthrottled, or measuring whether the exhaust gases are in the rangetypical of a diesel engine or a petrol engine, or checking the fuelpressure, or using a plurality of fuel type identifying methods andfurther assigning a weighting to the output of each of the plurality offuel type identifying methods, according to the type of fuel identifyingmethod and the output of the fuel identifying method, and summing theweightings and comparing the sum of the weightings to a predeterminedthreshold, to decide the fuel type of the vehicle.

According to a further aspect, the present invention provides a methodof estimating the mass of a vehicle; said vehicle having motionparameters comprising a vehicle speed parameter, a vehicle accelerationparameter and a maximum acceleration parameter, said vehicle having anengine, said engine having an engine capacity parameter and engineactivity parameters comprising an engine speed parameter, a powerparameter, a maximum power parameter and an engine load parameter, saidmethod comprising the step of determining a weighted or moving averagevalue of vehicle acceleration parameters taken during qualifying periodswherein at least one of the motion parameters and/or at least one of theengine activity parameters are within a predetermined range and usingsaid weighted or moving average value of vehicle acceleration toestimate the mass of the vehicle.

According to a further aspect, the present invention provides apparatusfor estimating the mass of a vehicle having an engine, said apparatuscomprising; means to determine motion parameters of the vehiclecomprising a vehicle speed parameter, a vehicle acceleration parameterand a maximum acceleration parameter, means to determine an enginecapacity parameter and engine activity parameters comprising an enginespeed parameter, a power parameter, a maximum power parameter and anengine load parameter, means to determine a weighted or moving averagevalue of vehicle acceleration parameters taken during qualifying periodswherein at least one of the motion parameters and/or at least one of theengine activity parameters are within a predetermined range and meansfor using said weighted or moving average value of vehicle accelerationto estimate the mass of the vehicle.

According to a further aspect, the present invention provides a methodof estimating the fuel consumption of an engine in a vehicle, saidmethod comprising the steps of obtaining or estimating an air flowthrough said engine; calculating a provisional fuel mass estimate bydividing the obtained or estimated air flow by a stoichiometric ratioassociated with the fuel type; estimating the fuel consumption bydividing said provisional fuel mass estimate by an oxygen contentparameter derived from an analysis of exhaust gases.

According to a further aspect, the present invention provides apparatusfor estimating the fuel consumption of an engine in a vehicle comprisingmeans for obtaining or estimating an air flow through said engine; meansfor calculating a provisional fuel mass estimate by dividing theobtained or estimated air flow by a stoichiometric ratio associated withthe fuel type; means for estimating the fuel consumption by dividingsaid provisional fuel mass estimate by an oxygen content parameterderived from an analysis of exhaust gases.

According to a further aspect, the present invention provides a methodof estimating the fuel consumption of a vehicle comprising collectingdata sets each of which relate to a particular different parameter andselectively processing selected data to establish the fuel consumptiononly if the value of some of the selected data or other data is of aqualifying value.

Said qualifying value is preferably between predetermined limits and isa substantially set value or is zero or substantially zero.

Preferably, the method includes determining an engine load reportingstrategy of an on board diagnostic system of the vehicle by processingdata collected when the vehicle is idling.

Preferably, the method includes determining the type of fuel used by thevehicle by processing data to provide the power of an engine of thevehicle which has been or is being collected when the vehicle istravelling at a substantially constant speed.

Preferably, the method includes determining the peak acceleration of thevehicle by processing data collected when the speed is less than asubstantially set value.

According to a further aspect, the present invention provides apparatusfor estimating the fuel consumption of a vehicle comprising meansadapted to collect data sets, each of which relate to a particulardifferent parameter and means adapted to selectively process selecteddata to establish the fuel consumption only if the value of some of theselected data or other data is of a qualifying value.

Preferably, said qualifying value is between predetermined limits and isa substantially set value or is zero or substantially zero.

Preferably, the apparatus includes means adapted to determine an engineload reporting strategy of an on board diagnostic system of the vehicleby processing data collected when the vehicle is idling.

Preferably, the apparatus includes means adapted to determine the typeof fuel used by the vehicle by processing data to provide the power ofan engine of the vehicle which has been or is being collected when thevehicle is travelling at a substantially constant speed.

Preferably, the apparatus includes means adapted to determine the peakacceleration of the vehicle by processing data collected when the speedis less than a substantially set value.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred aspects of the invention will now be described, by way ofexample only, with reference to the accompanying drawings in which:

FIG. 1 illustrates the steps of a first process relating to estimationof fuel consumption.

FIG. 2 illustrates the steps of an estimating fuel consumption processaccording to a second embodiment.

FIG. 3 illustrates the steps of estimating for estimating a total power.

FIG. 4 illustrates an implementation of fuel consumption estimationaccording to an embodiment of the invention.

FIG. 5 illustrates an implementation of fuel consumption estimationaccording to an alternative embodiment of the invention.

FIG. 6 illustrates the step of establishing qualifying periods accordingto an embodiment of the invention.

FIG. 7 illustrates a mass estimation module according to an embodimentof the invention.

FIG. 8 illustrates a mass estimation module with limitation and limitselection modules according to an embodiment of the invention.

FIG. 9 illustrates a frontal area estimation module according to anembodiment of the invention.

FIG. 10 illustrates a frontal area estimation module with limitationmodule according to an embodiment of the invention.

FIG. 11 illustrates the steps in determining the engine load reportingstrategy according to an embodiment of the invention.

FIG. 12 illustrates an engine load reporting strategy determinationmodule according to an embodiment of the invention.

FIG. 13 illustrates a fuel type detection module according to anembodiment of the invention.

FIG. 14a illustrates a further embodiment of the invention.

FIG. 14b illustrates another embodiment of the invention.

FIG. 15a illustrates yet another embodiment of the invention.

FIG. 15b illustrates another embodiment of the invention.

FIG. 15c illustrates another embodiment of the invention.

FIG. 15d illustrates another embodiment of the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

In accordance with one embodiment and set out in FIG. 1, a method ofestimating a fuel consumption provides for dynamically estimating a fuelconsumption during a particular time interval of a journey, and forsuccessive time intervals.

One way of calculating or estimating fuel consumption is based on thefuel mass processed by the engine. By obtaining a value for the air flowthrough an engine, we can estimate first the quantity of oxygen flowingthrough the engine and second, by for example analysing exhaust gases,the amount of oxygen that remains unburnt. Thus we can estimate theamount of oxygen burnt. We assume the oxygen not present in the exhaustgas is burnt so consequently we can work out, once the fuel type isknown, what quantity of fuel has been used. In particular, in accordancewith this method, airflow through an engine may be obtained or estimatedfor a particular time interval, and for successive time intervals,throughout the journey. This air flow may be obtained or estimated basedon data, such as manifold absolute pressure and temperature, acquiredfrom an On Board Diagnostics System (OBD), for example, data acquired ateach reporting cycle of the OBD operation, and such cycles may definethe time interval covered by the fuel consumption estimate.Alternatively, air flow may be obtained from the maximum air flowsensor, if present. A provisional estimate of a fuel mass beingprocessed by the vehicle during each time interval may then be obtainedby dividing such an air flow by a known stoichiometric ratio associatedwith the type of fuel being consumed. In particular, a fuel consumptionvalue may then be estimated from the fuel mass value and an oxygen valueobtained from analysis of the exhaust gases. The exhaust gases containoxygen which has passed through the engine and remains unburnt. In anembodiment of the invention, the oxygen value is taken from an oxygensensor, such as a lambda sensor. In an alternative embodiment, theoxygen value is obtained from a look-up taken, the value being chosen onthe basis of vehicle type and current engine load.

The quantities of such unburned oxygen may be used, to derive the fuelmass estimate, and estimate fuel consumption for each time interval.This provides a means to estimate, during each sample period, the fuelconsumption, so that for any given journey a fuel consumption may becalculated instant-by-instant throughout the journey. Thus a dynamicvalue for fuel consumption at a particular cycle of the OBD, can beestimated, and in addition a dynamic value for fuel consumptionthroughout a journey can be calculated.

While this provides a useful method of obtaining a fuel consumptionestimate, it may not always be available or suitable.

FIG. 2 sets out a further embodiment of the present invention, for usewhen this method is not available or suitable. In accordance with thisembodiment further means may be provided to estimate fuel consumption,and these means may be available, instead of, or as a supplement to, theair flow method.

The further means provide for dynamically estimating, for each timeperiod determined by cycles of the OBD, a total power usage of thevehicle during that time period. Fuel consumption is then estimatedbased on calorific values of the fuel and transmission efficiencies ofthe vehicle, in accordance with the following equation:

Fuel consumption=(total power usage)/(fuel calorific value×engineefficiency)  1:

Two of these parameters, fuel calorific value and engine efficiency, canbe established conventionally.

The total power usage in accordance with the present invention isestimated based on several components, as shown in FIG. 3:

A rolling power component, being the power expended to overcome thefriction of the road.

An aerodynamic power component, being the power expended to overcome airresistance, and.

An acceleration power component, being the power used to increase thespeed of the vehicle.

These components are related by the following equation:

total power usage=Rolling power+aerodynamic power+accelerationpower.  2:

The three components listed may be described in the following way:

The rolling power component may be summarised by:

Rolling Power=Coefficient of Friction×Vehicle Mass×9.81×Speed  3.

The aerodynamic power component may be described as follows:

Aerodynamic Power=(0.5×1.202)×Coefficient Drag×Frontal Area×Speed³  4:

The acceleration power component may be found from:

Acceleration Power=Acceleration×Vehicle Mass×Speed  5:

In respect of the factors contributing to the rolling power componentequation above it is clear that other factors will also be relevant, andfor example a gradient coefficient, which is an estimate of the averagegradient of the roads of a particular country or region in which thejourney is made, may be used. Alternatively a gradient detector or othermeans may be relied upon.

Turning to the components set out in equation 3 we consider first speed.The value for speed may be provided, by the OBD or perhaps by othermeans.

We consider next the coefficient of friction. The coefficient offriction will be a fixed value provided to equation 3. A typical valueof the coefficient of friction is 0.007, although the person skilled inthe art will appreciate that different values may be used according tothe road surfaces encountered and that in alternative embodiments of theinvention, different values of this coefficient may be used according toconditions. For example the gradient coefficient has the purpose ofmaking allowance for the fact that frictional force will be reduced onslopes due to the reduction in the reaction force. A typical figure forroads in the United Kingdom is 0.65, which reflects the average gradientof British roads. The person skilled in the art will appreciate thatthis figure may be varied according to where the vehicle is typicallytravelling. Other embodiments may include options for a used input valuewhich reflects the country or region of a country or the type of roadson which the vehicle is typically used. A further embodiment wouldensure that a check is made on the slope on which the vehicle istravelling before an estimate is made of the frontal area of thevehicle. An option would be for example to only record readings when avehicle was travelling along a substantially level section of road. Analternative embodiment would provide an estimate of the current slope.The invention is not limited to any one method of estimating gradient orcircumventing the effects of gradient.

We consider next a further constant, the acceleration due to gravity.This is provided to convert the vehicle mass figure into a force, inorder to determine or estimate the reaction force and hence thefrictional force on the vehicle. Although this is a constant, the personskilled in the art will appreciate that different levels of accuracy maybe used in the recording of this factor.

This leaves the value for vehicle mass. There are many ways to arrive ata value for vehicle mass. For example a user input may be relied upon,force and acceleration readings may be relied upon and a least squaresmethod utilised, or other conventional means.

In accordance with the present invention, the mass may be estimated byestimating the force supplied to the wheels at particular qualifyingperiods during vehicle use, for example, at periods of peakacceleration. This will be discussed later.

In respect of factors contributing to the aerodynamic power component,in respect of equation 4, we consider first the coefficient of drag. Thecoefficient of drag will be a fixed value provided to equation 4. Thespeed of the vehicle may be taken from the On board diagnostics (OBD)system or from a Global Positioning Satellite (GPS) system, or othermeans.

We consider next the remaining parameter, the frontal area of thevehicle. The frontal area of the vehicle may be a conventional userinput value. In an alternative method in accordance with the presentinvention the frontal area, or in particular the effective frontal area,is estimated. The effective frontal area is estimated by identifyingperiods of steady state, i.e. non accelerating, motion, and finding anestimate for the aerodynamic power on the left hand side of equation 4,by establishing the difference between the rolling power and the totalpower of the vehicle. All the parameters of the equation will then beknown and used to establish the frontal area, or effective frontal area,of a vehicle. This will be discussed in detail later.

In respect of the factors contributing to the acceleration powercomponent in equation 5 above, we consider first the acceleration of thevehicle.

The acceleration of the vehicle may be acquired, for example, from theOBD or from a Global Positioning Satellite (GPS) system, or other means,and the speed and mass have already been referred to above.

Once these components have been established we can provide a value fortotal power usage in accordance with equation 2 above. Once a value fortotal power usage has been established we can estimate a value for fuelconsumption.

The total power usage provided to equation 2 may be a value calculatedat each time interval during the course of a journey, therefore aninstantaneous fuel use may be dynamically estimated at each timeinterval of a journey.

An example of the implementation of the above method according to anembodiment of the invention is shown in FIG. 4. FIG. 4 shows foursub-modules, the rolling power module 401, the aerodynamic power module402, the acceleration power module 403 and the fuel calculation module404. Nine inputs are provided, Vehicle speed 405, Vehicle mass 406,Coefficient of friction 407, Gradient coefficient 408, Coefficient ofdrag 409, Effective Frontal area 410, Vehicle acceleration 411, FuelCalorific value 412 and engine efficiency 413. The outputs of the powermodules 401, 402 and 403 are summed and provided to fuel calculationmodule 404.

An example of the implementation of the above method according to afurther embodiment of the invention is shown in FIG. 5. This embodimentwill now be discussed in detail. FIG. 5 includes Mass Estimator Module501, Frontal Area Estimator Module 502 and Engine Load ReportingStrategy Module 503. As set out in FIG. 5, the mass estimator moduleprovides information to the rolling power module, which reflects thatthe rolling power component relies on a value for mass. The frontal areaestimation module and the engine load reporting strategy module provideinformation to the aerodynamic power module which reflects that theaerodynamic power component relies on a value for frontal area and onthe engine load reporting strategy. The acceleration power componentrelies on a value for mass.

The frontal area estimator module 502 and the Engine Load ReportingStrategy module 503 will be discussed later.

As seen from FIG. 5, and set out herein in more detail, the massestimator module has seven inputs: vehicle speed 405, vehicleacceleration 411, engine speed 503, engine load 504, an HGV indicator505, fuel type indicator 506 and a maximum power 507.

The frontal area estimator has nine inputs: vehicle speed 405, vehicleacceleration 411, engine speed 503, engine load 504, an HGV indicator505, fuel type indicator 506 and a maximum power 507, an engine loadreporting indicator 508, received from module 503 and a rolling powerinput 513, received from module 401.

The engine load reporting strategy module has six inputs: vehicle speed405, engine speed 503, engine load 504, fuel type indicator 506, enginecoolant temperature 510 and engine on indicator 511.

Considering first the vehicle mass: as discussed, a value for thevehicle mass is needed at least for equation 3. A mass value may beprovided by estimating the force supplied to the wheels at certaintimes, for example during appropriate qualifying periods. In this case,the appropriate qualifying periods are periods of peak acceleration. Theprocess of identifying qualifying periods is illustrated in FIG. 6. FIG.6, steps 602-606 outline the process of identifying appropriatequalifying periods to estimate the mass and hence calculate the rollingresistance power component of equation 3. Periods of peak accelerationare selected as appropriate qualifying periods, in particular as it canbe assumed that for such periods the engine is working at maximum power.Therefore relying on F=MA, if a known maximum value for force, and amaximum value for acceleration (peak acceleration) are used, then weshould be able to derive the mass by Mass=Force (max)/Acceleration(max).

FIG. 6 shows, in step 601, that when at least one motion or engineparameter is within a predetermined range, a qualifying period may betriggered.

In the present case, when it is detected that the engine has achievedpeak power, a qualifying period for the peak acceleration calculationbegins.

Periods where the engine has achieved peak power may be identified usingthreshold values in accordance with steps 601 of FIG. 6. In particular,the thresholds are selected to determine periods of peak accelerationwhilst the vehicle is in first gear. Readings of peak acceleration aretaken, for example from the OBD, and an incremental learning algorithmis implemented which updates the currently held value of peakacceleration. The cases where no value for peak acceleration is held isdiscussed later.

As stated, estimation of the mass is performed by taking the estimatedpeak acceleration and a figure for the force applied.

The figure for the force applied can be obtained by conventional meansfrom the peak power figure, by division by the vehicle velocity. Thepeak power figure is adjusted, using figures for transmission efficiencyand transmission loss, to convert the maximum power into a figure forpower at the crank.

In an alternative embodiment, empirically obtained conversion factorsare used to convert the figure for acceleration into one for power/mass.The power figure is then used with this value to give an estimate forthe mass of the vehicle.

While this broadly discloses this method of estimating the mass of avehicle, there are potential problems and these are discussed below.

For example, it may be that a mass figure will be needed prior to theoccurrence of a period of peak acceleration, and so an estimate of massbased on an empirically obtained relationship between engine size andvehicle mass may be incorporated into the system. A typically usedempirical relationship is that 1 cc of engine size roughly correlateswith 1 Kg of vehicle mass, but other values are contemplated.

In addition, a sanity check is included to ensure that the valuesprovided are sensible and so in addition to the recognition of peakacceleration and the learning algorithm, additional optional featuresare available which include a comparison of the mass estimate withpredetermined limits of mass, both minimum and maximum, for differenttypes of vehicles. For example, comparison can be made with a usersupplied mass figure. Alternatively, or in addition, a further value,providing a maximum and a minimum figure based on a percentage errorrange for the mass, may also be incorporated into the mass estimationsystem.

Additionally, upper and lower limits for mass, determined by the type ofvehicle are also contemplated to provide for a realistic range for themass, rather than insisting on an exact reading, and this is discussedlater.

An HGV indicator may also be relied upon. The HGV indicator identifiesthat the vehicle is a heavy goods vehicle, which is useful both fordetecting peak acceleration and also in power estimation, primarilybecause reference values for comparison of engine speed and vehicleacceleration, and the transmission efficiency, are set depending onwhether the vehicle is an HGV.

Generally HGVs have higher efficiency values, due simply to their higherpower, and so the HGV indicator is used to select between transmissionefficiency values, among others. Put simply, in order to calculate peakacceleration, a mechanism for identifying peak acceleration periods isemployed, in addition to a mechanism for selecting thresholds dependenton whether the vehicle is an HGV.

As discussed, a calculation of peak acceleration requires anidentification as to a qualifying period, for example when near peakacceleration is occurring, and also identification as to when thequalifying period ends, when the acceleration has ended and theacceleration is dropping below the peak.

While a mass value can be derived for vehicle mass using Mass=Force(max)/Acceleration (max) this assumes that substantially all the forceis directed to accelerating the vehicle. However this may not be thecase, either because the force is perhaps combatting air resistance (ifthe vehicle speed is high), or the vehicle may be going down a hill, ormany more reasons.

The optimum occasion to rely on F(max)=Mass×Acceleration (max) to obtaina value for mass is when the vehicle is in first gear (i.e. at lowspeed) on the flat. We can rely on FIG. 6 item 601 to select thresholdvalues for motion or engine parameters to identify appropriatequalifying periods which indicate this particular circumstance.

Such variables can include, in addition to peak power, engine load,engine speed, and vehicle speed, as set out in FIG. 5. To indicate thevehicle is in first gear on the flat, the values of each of thesevariables must satisfy a threshold condition. For example, anacceleration threshold, typically 0.2 ms⁻² for HGV's and 0.5 ms⁻² forother vehicles, may be provided for comparison with the actual vehicleacceleration; engine load must be greater than a given percentage of themaximum engine load, for example it may be 80% of maximum engine load;and the required levels of engine speed are generally set also and maybe in the region of 1500 rpm for HGVs and 3500 for other vehicles,although all these values are exemplary only and variations arecontemplated.

The vehicle speed may also be checked.

Checking the vehicle speed will assist in indicating that the vehicle isaccelerating and not, for example, wheel spinning. A lower limitingspeed is entered into the model prior to use, which may be the region of20 Km/H, although other values are contemplated and fall within thescope of the invention. The lower limiting speed has the additionaladvantage that it helps to indicate that, for example, clutch slip isnot occurring. An upper limiting speed, typically in the region of 50KmH, but other values are contemplated, is also input before system useis initiated.

The levels, described, in combination with other values, indicate thatthe vehicle is in first gear and experiencing maximum acceleration, asrequired.

In an alternative embodiment of the invention, a GPS (Global PositioningSatellite) system is used to check that the vehicle speed correspondscorrectly with the wheel speed. In yet another embodiment, anaccelerometer may be used.

As stated, only periods of peak acceleration are of interest, and so itis necessary to identify the end of the qualifying period for peakacceleration.

The system may be adapted to monitor the acceleration parameters toidentify the end of a period of acceleration, when an end ofacceleration indication is issued.

In addition, within a given period of acceleration above the threshold,it is necessary to select the highest acceleration value achieved.According to an embodiment of the invention, this is achieved bysuccessively comparing a currently held value of the maximumacceleration with the acceleration recorded in the current time slot.

In particular, the purpose is to provide the value of the instantaneousacceleration of the previous timeslot if the vehicle is undergoing abovethreshold acceleration and a zero value if its acceleration is beneaththat threshold.

An important part of the invention is an incremental estimationmechanism module. This mechanism compares an instantaneous estimate ofpeak acceleration, with a value from the difference between a currentperiod of peak acceleration and a previously stored value. Thisdifference is then divided by a weighting factor and added or subtractedto the previously stored value to find a new estimated value. Aweighting factor of 3 is typically used, but the person skilled in theart will appreciate that different weighting factors may be used and thecurrent invention is by no means limited to any given weighting factor.

As part of the model, it is established that any incremental valueprovided for the adjustment of peak acceleration is betweenpredetermined limits. This ensures that the incremental value will be asensible one and will eliminate “outliers” in the increment values.Typical limiting values are based on the unladen weight of the vehicleand the maximum legal load, for example for an HGV, although it is notcontemplated that these values are limiting.

The incremental estimation mechanism referenced above provides for anincremental learning algorithm which will maintain a value of peakacceleration until a new value becomes available, at which time thevalue is replaced.

A further potential problem relates to the procedure where no value forpeak acceleration is available. In such cases it is useful to use aninitial estimate of the peak acceleration. Hence a check is carried outto establish whether a peak acceleration reading has been recorded andif not, allows the use of an estimate based on engine size, and perhapseffective power, to be used prior to the recording of a peakacceleration value. A typical method of checking if an above thresholdacceleration has occurred comprises checking if a peak accelerationindicator flag is set.

Alternatively, if the currently held value of peak acceleration is equalto zero, or other default value according to the constant used, this mayalso indicate that no period of above threshold acceleration has yetoccurred.

In a preferred embodiment empirical factors may also assist incalculating such a value, for example at least one empirical powerfactor. Such empirical power factors may be estimated by takingexperimental readings of the key parameters, namely, engine speed,engine load, vehicle speed and vehicle acceleration, and thendetermining a mass figure using the method described herein. This massfigure can be compared with the mass of a vehicle of known mass and thepower factors estimated by a process of iteration. Typical values forthe empirical power factors are 38.7 for the first power factor and0.2885 for the second power factor. Both of these values have beenobtained for diesel vehicles and are for systems in which the vehiclepower is provided in Pferdstarke (PS).

Different values are required for small petrol engines, due to the lowermass of their fly wheels and other moving engine parts. The personskilled in the art will appreciate that alternative values may be usedand these will be within the scope of the invention. The invention isnot limited to any given values for the power factors, nor even to agiven set of power value variables. For example in an alternativeembodiment of the invention, a polynomial relationship may be used togive improved accuracy in the relationship between engine size, powerand force.

Peak acceleration values combined with values for power, taken atconstant engine velocity, may provide for an indirect calculation offorce. Calculations may rely on, for example, engine power, HGVindicator and vehicle speed. In an embodiment of the invention, twovalues for transmission efficiency are provided, typically substantially0.9 for heavy goods vehicles and substantially 0.85 for other types ofvehicle, although these values are not limiting.

Thus methods have been disclosed for calculating a total engine powerfigure including a power loss figure relating to transmissionefficiency. Thereafter a simple calculation may be carried out to obtaina mass estimate figure.

As discussed, in order to ensure that the mass measurements are withinsensible limits, a further limitation step is provided to ensure thatthe mass reading provided is between reasonable limits for a given typeof vehicle. This maybe for example, for a heavy goods vehicle, theunladen weight of a typical HGV for the minimum value and the maximumlegal load for road haulage as the maximum value. The limitation moduleprovides an additional and optional check on the mass values.

The following example may more clearly describe the process:

Four groupings of engine size are provided, namely under 1900 cc,between 1900 cc and 4000 cc, between 4000 cc and 6500 cc and above 6500cc. In the case of an HGV, two sets of mass data are provided, dependingon whether the engine size is greater or less than 6500 cc. For eachoption, a minimum and a maximum value for weight is given. In the caseof non-HGV vehicles, three options are provided for the maximum value,and one for the minimum value. In an embodiment of the invention, thethree maximum values correspond to the maximum weights of a small car, a“4×4” and a light van respectively. The person skilled in the art willappreciate that different choices of vehicle and upper and lower limitvalues can be made without departing from the scope of the invention. Atypical set of options for the limitation module is shown in Table 1.

TABLE 1 HGV Engine size Fuel type Minimum weight Maximum weightYes >6500 19000 44000 Yes <6500 3600 21000 No >4000 3200 800 No >1900Diesel 3750 800 No >1900 Petrol 3200 800 No <1900 2500 800

Several steps are optionally included as part of such a limitationactivity. In one step, if the vehicle seems to be an HGV, the enginesize is compared with a reference value and an HGV indicator issued orconfirmed. This HGV indicator is used to select a minimum mass value,for either an HGV if the indicator flag is set, or for a lighter vehicleif the indicator flag is not set. On setting the minimum mass value foran HGV, engine size is also taken into account as the engine sizedetermines the minimum mass value of the HGV. For example, if the enginesize falls within a first value, a first minimum mass value is selected,and if the engine size falls within a second value, a second minimummass value is selected, and so on.

In addition, steps are carried out to obtain a maximum mass value. Inaddition to depending on engine size, the maximum mass value alsodepends on fuel type, and so the fuel type indicator may be relied uponin the maximum mass value calculation.

In particular a first maximum mass value may be selected if the enginesize is greater than a predetermined reference value and the fuel typeindicator indicates a diesel engine. This might indicate for examplethat the vehicle is a small van. If the engine size is greater than afurther engine size reference value and the engine uses petrol, then adifferent maximum mass value may be selected, and so on.

Such exemplary steps are carried out to provide confidence that the massestimation value is likely to be correct, by setting realistic minimumand maximum limits of mass.

Alternatively a user supplied vehicle mass may be used as an additionalcheck.

Details of the mechanism of the processes discussed are set out herein.In particular, FIG. 7 shows the mass estimation module 700 according toan embodiment of the invention. It comprises a peak accelerationdetection module 701, an incremental learning module 702 and a powerestimation module 703. There are 6 inputs into the system, engine speed503, engine load 504, HGV indicator 505, vehicle acceleration 411 androad speed 405. The HGV indicator 505 is used to select betweenreference values for comparison with the engine speed and vehicleacceleration, and the transmission efficiency, according to whether thevehicle is an HGV or other vehicle type.

The four motion and engine parameters 503, 504, 411, 405 are input intothe peak acceleration module 701, which determines whether the vehicleis close to peak acceleration. The power estimation module 703 has twoinputs, the HGV indicator 505 and the power input 704. The power inputis the power at the crankshaft. The HGV indicator is used to makeallowance for the different transmission efficiencies discussed above.

A Boolean value is output to the peak acceleration indicator 705 and theacceleration value is output at 706. If the peak acceleration indicator705 is equal to logical one then the acceleration value is passed on byswitch 707 to the incremental learning algorithm 702. If it is equal tological zero, then the zero value from 708 is passed on. The incrementallearning algorithm has three inputs, the peak power estimate 709, theroad speed 405 and an input of acceleration from the switch 707. It hasa single output, the estimate of vehicle mass 710.

The estimate of mass from the model will by its nature not be exact andtherefore in an embodiment of the invention, the mass reading is givenwithin error limits rather than an exact reading. If no engine powervalues are known then the mass limits are the maximum and minimum valuesdetermined by the limitation process.

FIG. 8 therefore shows a second embodiment with additional modules, thelimitation module 801 and the limit selection module 802. The limitationmodule provides for upper and lower limits of mass, determined by thetype of vehicle. The limit selection module 802 gives upper and lowervalues of the mass estimates, thus providing a realistic range ratherthan an exact reading. The upper and lower limits of the mass estimateare supplied to outputs 803 and 804 respectively.

Considering now the frontal area. As shown above, Equation 4 relates tothe aerodynamic power component, and relates to a coefficient of drag, afrontal area, and speed. The coefficient of drag is a predeterminedvalue, and there are several ways to identify the speed, not least usingthe OBD. This leaves the frontal area. The frontal area is related toseveral parameters such as: vehicle speed 405, vehicle acceleration 411,engine speed 503, engine load 504, HGV indicator 505, fuel typeindicator 506, maximum power 507, an engine load switch value, and arolling power.

A value for engine load is obtained from the OBD, however to use thisvalue effectively we need to detect an engine load reporting strategy,i.e. what the reading obtained from the OBD actually means, and thiswill be discussed later.

Returning to the frontal area. FIG. 6 steps 608-611 outline the processof identifying appropriate qualifying periods for estimating the frontalarea. FIG. 6 shows in step 601, that when at least one motion or engineparameter is within a predetermined range, a qualifying period may betriggered. In the present case we rely on periods of steady state,during which we calculate a figure for power supplied at the crank. Thisprocess utilises a steady state detection, with an incremental learningprocess as shown in FIG. 9. We measure the power at the crank at periodsof steady state as we then know that the power supplied is not beingprovided to accelerate the vehicle, but is substantially directed toovercoming air resistance in particular a vehicle is in a steady stateif it is not undergoing significant acceleration and is on asubstantially flat surface. It is contemplated that a speed of, forexample, around 100 Km/h, such as for example 90-110 km/h, may be usedfor light duty vehicles, with lower values for Heavy Goods Vehicles. Inaddition, a check may be carried out to determine whether the vehicle isin the correct gear. This ensures at least that energy is not beingexpended due to being in the wrong gear.

A current estimate of power in such a steady state is then identified.This estimate of power relies on the engine load, and this may beobtained from the OBD. This will be discussed in more detail later.

As stated in order to complete the calculation of the frontal area weneed to establish the engine load 504 for the vehicle. The followingsets out briefly how the engine load may be determined.

There are two major strategies by which On Board Diagnostics (OBD)systems report the engine load. Diesel engines usually report thepercentage of maximum torque for a given engine speed, which gives apercentage of maximum power of the engine, whereas petrol engines,depending on vehicle type, may provide the percentage of peak power,i.e. the instantaneous power at that time. Accordingly, in an embodimentof the invention, the strategy being used by the vehicle is identifiedand an indicator provided to reflect the engine load reporting strategyemployed, so that the engine load can be determined.

The engine load reporting strategy is discussed in detail later.

Once we have a value for the engine load we can use it to establish thefrontal area. In particular, the current power supplied by the engine isestimated by multiplying the peak power by the percentage of peak powercurrently being used. This percentage may be obtained from the engineload value reported by the OBD. It is not necessarily clear, in anyvehicle, how the engine load will be reported. For example in an OBD inwhich the load is reported as a percentage of maximum power, a simplemultiplication of the peak power by the engine load or equivalent figuresuffices. However, if the reported engine load value is a percentage ofthe torque at the given engine speed, then an engine load valueadjustment must be made to encompass this alternative strategy.

In an embodiment of the invention, the engine load value adjustmentcomprises multiplying the power value by a factor equivalent to1/(engine speed at peak power). A typical value for the engine speed atpeak power is 4500 RPM, but other values are contemplated.

Depending on the way the engine load is reported, a value for thecurrent power provided at the crank is established.

The result is then normalised to a standard vehicle speed, and thenormalisation may include a fixed value for speed, or different valuesdepending on vehicle type, or user supplied values.

Thus a figure for power, normalised for a chosen vehicle speed,typically but not limited to 100 Km/H is provided. It can also beestablished if the vehicle is moving in a steady state on asubstantially flat surface. When it has been decided that the vehicle isin the required steady state, and a qualifying period may be inoperation, in accordance with FIG. 6, initiation of the incrementallearning algorithm may proceed.

Details of the qualifying period for the aerodynamic power estimationwill be discussed later. First we discuss the incremental learningmodule. The incremental learning module relies upon three components,the averaging component, weighting component and the end of steady stateidentifier, and on initiation required calculations may be carried out.

The averaging module calculates the average value of the input powerover a set period of time. At the end of each averaging period, thiscalculated value is sent to the weighting module, which calculates aweighted average between this value and the value obtained from previousaveraging periods. This continues during the steady state period.

The averaging module also maintains a count of the number of samplesaveraged, which is reset after a set period. In an embodiment of theinvention, 255 samples are taken before the rest, but the person skilledin the art will appreciate different numbers of samples may be taken andthe invention is not limited to the number of samples taken in eachbatch. Two memories are provided for the performance of the averagepower input, the sample count and a sum of the power input.

At the end of a sample period all values are set to zero.

The weighting module is relatively conventional and is provided with anaverage power reading by the averaging process during the steady stateperiod. In addition, a check is provided, including upper and lowerlimits on the weighted average value to provide confidence in the valuesprovided.

When it is detected that the steady state condition no longer applies,the qualifying period ends, and the end of steady state identifier flagis set, which terminates the calculation.

The person skilled in the art will appreciate that there are othermethods by which a suitable average value may be obtained. In anotherembodiment, each power value on every time slot is used for a weightedaveraging, without using the suggested intermediate averaging processdiscussed. In yet another embodiment, a simple average is taken of allthe power values obtained without any weighting process. The inventionis not limited to any particular method of calculation of the averagepower value.

As discussed, a weighted or moving average of the power value derived iscalculated by the incremental learning algorithm. Such averaging isperformed over fixed size sample periods, and at the end of such asample period, an average total power value is provided and a new sampleperiod function is initiated.

As set out above, we can estimate a figure for the rolling power of thevehicle, estimated by a rolling power module as discussed above. Adifference between the supplied rolling power of the vehicle and thecurrent power value may be established so that a frontal area, oreffective frontal area, based on the aerodynamic power and also onempirically obtained values for the drag coefficient, may be calculated,in particular from equation 4.

It is often sensible to carry out a check to provide confidence in anyvalue calculated. This check seeks to ensure that the estimates of theaerodynamic power are within certain limits, based on the knownaerodynamic drag of certain vehicles.

Returning now to qualifying periods for establishing steady state.

As stated, the purpose of the steady state detection module 902 is toidentify periods in which the vehicle is being driven at a constantspeed, typically within the range of 90 km/h-110 km/h, more particularlyaround 100 km/h, but not necessarily limited thereto. It is importantthat the vehicle should not be accelerating or decelerating to ensurethat all power is expended to overcome the effect of the frontal areaand hence establish an estimate for the frontal area. However, it wouldnot be possible to require calculations to be performed only when thevehicle had exactly zero acceleration, so a small range, typicallybetween −0.02 and 0.02 MS⁻² is counted as being zero acceleration,although this range is not limiting. A secondary check on steady state,to ensure that the period is, in fact, in a steady state, is to look atthe engine load. The vehicle should not be coasting, nor should thethrottle be wide open, and the latter combined with a near zeroacceleration would indicate that the vehicle was most likely to climbinga steep hill. To provide confidence that a steady state has beendetected, the engine load should therefore be within the range ofsubstantially 30% and substantially 70% of maximum load. A furthersecondary check for steady state is to look at the engine speed, forexample to see that the vehicle is in the correct gear. For this to bethe case, the engine speed should lie between two threshold values, thelower threshold being typically higher for a petrol engine compared witha diesel engine. The engine speed will depend on whether the vehicleuses diesel or petrol fuel and typical values for the respectivethresholds are substantially 4500 RPM for the upper threshold, and, forthe lower threshold, substantially 2000 PM for a diesel engine andsubstantially 2500 for a petrol engine.

Therefore the first check as to whether the vehicle is in facttravelling at a steady state is to check that the vehicle speed iswithin the required range as discussed already, and the mechanism forthis check is largely conventional, depending however on the vehiclespeed, comparing this with reference values as discussed. It should benoted that lower values of these thresholds would be required for heavygoods vehicles due to legal limitations on their speeds. The personskilled in the art will appreciate that these reference levels areexemplary only and different levels may be used whilst being with thescope of the invention.

As stated the next check as to whether the vehicle is in fact travellingat a steady state is to check that the acceleration is within requiredlimits, in particular that the vehicle is very close to constant speed.

The final steady state check is to establish that the engine speed iswithin acceptable limits, and this indicates that the vehicle is in thecorrect gear.

The power at the crank also takes account of at least one empiricallydetermined power factor(s), which model the power loss or losses due totransmission. One empirical factor is subtracted from the engine powerand in the preferred embodiment of the invention is the same for allvehicle types. A further power factor is a multiplicative efficiencyfactor, which differs according to whether the vehicle is an HGV or alight duty vehicle. The person skilled in the art will appreciate thatit is possible to refine these values according to vehicle type or make,or to allow the user input of this value and the invention is notlimited to any one method of allowing for transmission power losses. Inthe preferred embodiment therefore, the power at the crank is determinedby the subtraction of a first empirical power factor and multiplicationby a second empirical power factor. Selection of the second empiricalpower factor may be based on the type of vehicle, for example HGV orlight vehicle.

There are alternative methods of providing a figure for the power at thecrank, such as for example multiplication or subtraction by a singletransmission factor or by direct estimation of the power at the crank.Typically the value of the first power factor is substantially 10 PS(˜7.5 KW) and the values of the second power factor are substantially0.9 for an HGV and 0.8 for a light duty vehicle. The person skilled inthe art will appreciate that these values may be varied and theinvention is not limited to any particular values of the power factors.

The frontal area may now be calculated, for example by reverseengineering from the aerodynamic power calculated in a steady state ataround 100 Km/h. This figure may then be used for estimation of theaerodynamic resistance at different speeds and accelerations. Theformula for effective area is obtained by rearranging equation 4 aboveand is given in equation 7:

$\begin{matrix}{{Area} = \frac{2 \times {Power}}{\rho \; C_{d}v^{3}}} & {{Equation}\mspace{14mu} 7}\end{matrix}$

Where p is the density of the fluid through which an object is moving, vis the velocity of the object, A is the effective area of the object andC_(d) is the drag coefficient.

A figure for the aerodynamic resistance is obtained by subtracting theestimate of rolling resistance obtained from the Rolling Powercalculation carried out above. The estimate of aerodynamic power is usedin the Frontal Area Calculation together with the parameters set outabove.

We now discuss the arrangement in more detail.

FIG. 9 illustrates a frontal area estimation module according to anembodiment of the invention. It comprises a power module 901, a steadystate detection module 902, an incremental learning module 903,subtractor 904 and a frontal area calculation module 905. The powermodule provides a figure for the power at the wheels, based on valuesprovided for engine speed 503, engine load 504, engine power 704, HGVindicator 505, vehicle speed 405 and engine load switch 508, whichindicates the engine load reporting strategy.

The power at the wheels 906 is supplied by power module 901 to theincremental learning module 903, which is activated when an indicator907 is received from the steady state detection module 902. The steadystate detection module receives current values for engine speed 503,vehicle speed 405, acceleration 411, engine load 504 and fuel type 506.The current estimate of power in the steady state is supplied to input908 of subtractor 904. The Incremental learning algorithm 903 performs aweighted or moving average of the power value obtained from the PowerModule 901. At the end of such a sample period, an average total powervalue is forwarded by the Incremental Learning Module 903 to subtractor904. Additionally, an end of sample period indicator 909 is sent fromthe Incremental Learning Module to the Steady State Detection Module inorder to start a new sample period.

A rolling resistance power is supplied to input 513 and is subtractedfrom the output 908 of the Incremental Learning Module 903, to give anestimate of the aerodynamic power to Effective Frontal Area Calculator905. Effective Frontal Area Calculator 905 calculates the effectivefrontal area based on the aerodynamic power and empirically obtainedvalues for the drag coefficient.

In a preferred embodiment of the invention, a limit is introduced forthe upper and lower values of the aerodynamic power. The limits relateto values for a variety of vehicles, including large or small cars,light vehicles, or an HGV vehicle. Accordingly, FIG. 10 illustratesanother embodiment, which further comprises a limitation module 1000,which ensures that the estimates of the aerodynamic power are withincertain limits, based on the known aerodynamic drag of certain vehicles.

It is contemplated that intermediate values, such as area multiplied byone or more of the drag coefficient, vehicle speed cubed, fluid densityor the constant 0.5, may be used and suitably converted using equation 7or an appropriate derivative. The person skilled in the art willappreciate that any of these methods can be used without affecting theembodiment of the invention.

As set out above, critical to the estimation of the Effective FrontalArea is the engine load reporting strategy, and we will now discuss theEngine Load Reporting Strategy in detail. As explained above, the engineload may be provided as a percentage of the maximum torque or apercentage of the torque at the given engine speed. In an embodiment ofthe invention, the reporting strategy is entered by the user. In analternative embodiment, it is deduced by examination of the OBD outputparameters.

At high engine speed and load, the two reporting strategies will givereadings which are very close to each other as the engine is working atits maximum and an engine power at the given speed is close to a maximumengine power for the vehicle. In contrast, the point of greatestcontrast in reported engine load values is when the engine load is atits lowest. This latter point will occur when the engine is idling.

Therefore in a preferred embodiment, the Engine Load Reporting Strategywill be deduced by identifying periods, idling qualifying periods, inwhich the engine is idling and comparing the engine load with apredetermined threshold. This process is set out in FIG. 11. The processof identifying qualifying periods for determining the engine loadreporting strategy are illustrated in FIG. 6, steps 612 to 614.

The idle speed (generally measured in revolutions per minute, or rpm, ofthe crankshaft) of an internal combustion engine is the rotational speedof the engine when it is uncoupled from the drive train and the throttlepedal is not depressed. At idle speed, the engine generates enough powerto run reasonably smoothly and operate its ancillaries (water pump,alternator, and, if equipped, other accessories such as power steering),but usually not enough to perform useful work, such as moving anautomobile. For a passenger-car engine, idle speed is customarilybetween 600 rpm and 1,000 rpm. When idling, an engine typically has aload of a few percent of maximum power, normally less than for example8%, and the engine speed will also be low at idling, for example thepercentage of the maximum power for the given engine speed willtypically be around 20-30 percent.

FIG. 11 shows the parameters to be considered in determining if anengine is idling. For example, periods in which the engine is idling areidentified by checking the engine speed and comparing this to athreshold value, the idle speed threshold. A default value for thethreshold is used as a starting point and adjustments are then made toit to allow for engine temperature (related to the length of time theengine has been running), engine size and fuel type.

We check fuel type because diesel engines usually have higher idlingspeeds than petrol engines. We check engine size because smaller engineshave higher idling speeds than large ones. We check the temperaturebecause, in general, the hotter the engine, the lower the idling speedwill be. It may be that no correction is made for the length of time theengine has been running, or coolant temperature may not be relied upon.

We must also take into account that a minimum engine speed must also beexceeded to ensure that the engine is in fact running.

To avoid mistaking an engine idling circumstance, for example where avehicle may be coasting downhill, or moving slowly forward with nopressure on the throttle, a further check may be carried out on vehiclespeed, in which the vehicle speed is taken from the OBD system, a zerovalue confirming an idle condition.

In addition we also need to consider that if a vehicle is being held onthe clutch on a slope, the vehicle may have zero speed but the enginemay not be idling. This can be identified by comparing the engine loadwith a threshold dependent on fuel type. Typical values for thethresholds are 70% load for diesel engines and 23% load for petrolengines. However the invention is not limited to any particular valuesfor these thresholds.

Once it has been established that an engine is idling, we can implementto the method of determining the engine load reporting strategy.

As discussed, if it is determined that the engine is idling and thereported engine load is less than a threshold, then the reportingstrategy is likely to be a percentage of maximum torque, whereas if itis above the threshold the reporting strategy is likely to be apercentage of power at the given engine speed. An indicator as to whichstrategy has been detected is then passed on to a persistency check andlatch function. This seeks to ensure that the strategy is only recordedas correct if the indicator has been set to the level for a given timethreshold, i.e. a persistency check is carried out, and if passed theengine load reporting strategy is fixed.

As stated, the running time and temperature of the engine is alsorelevant and if the running time is less that a pre-set threshold (theidle time threshold), the temperature of the coolant, obtained from theOBD system, may be used to adjust the threshold.

In addition the engine load is checked against a predeterminedthreshold, as the engine load depends on whether the engine uses dieselor petrol, and exceeding the threshold provides a strong indicationthat, even if the vehicle speed is zero, the engine is not idling, butmay be on a slope held on the clutch. A clutch check utilises the fueltype indicator, and engine load, to select a diesel or petrol clutchthreshold, although other methods are also contemplated.

Thus, the engine load reporting strategy is calculated by determiningwhether the engine is idling and then determining whether the engineload is greater than a given threshold. The method also checks theengine speed to see if it is below the idle speed threshold calculatedby this process, whether the engine is running, indicated by whether theengine speed is above a required threshold, whether the clutch checkmodule has indicated that the vehicle is being held on its clutch, andthe vehicle speed. If the engine is determined to be switched on, isoperating at below the calculated idle speed threshold and the vehiclespeed is zero, then the engine is assume to be idling.

In more detail, as stated, as an overall review, in order to determinethe engine load reporting strategy, a period, the idling qualifyingperiod, in which the engine is idling, must be identified. If duringthis period, the reported engine load is small, typically a singlefigure percentage, then the reporting strategy is taken to be to statethe percentage of maximum torque. If the reported engine load is largerthan this, then the reporting strategy is taken to be to state thepercentage of engine load at the given engine speed. The engine isidentified as idling if the vehicle speed is zero, the vehicle is notbeing held on the clutch and the engine speed is less than a giventhreshold. The threshold is determined taking into account the fueltype, the engine temperature, the engine size and the length of time forwhich the engine has been running, although other means arecontemplated. For example, in an embodiment, a fixed threshold may beused. In a further embodiment, a threshold altered to allow for enginesize only may be used. In yet a further embodiment, only adjustments forengine running time may be used, either as a threshold running time oran adjustment based on engine temperature.

In further detail and with reference to the drawings, the stages of thedetermination of the engine load reporting strategy are illustrated inFIG. 11 and an engine load reporting strategy detection module accordingto an embodiment of the invention is illustrated in FIG. 12. The engineload reporting strategy detection module is set out in FIG. 12, whichshows six component modules including a time and temperature module1203, a fuel type module 1204, an engine size module 1205, a clutchcheck module 1206, an idling check module 1207, and a persistency checkand latch module 1208. These modules have seven inputs, engine onindicator 512, fuel type indicator 506, engine coolant temperature input1201, engine speed 503, engine load 504, vehicle speed 405 and OBDsample time 1202.

Starting with the Time and temperature module 1203, this module checkswhether the engine has been on for more than a threshold period of time.In an embodiment, if the engine has not been running for more than athreshold time, then the engine temperature, measured by reference tothe coolant temperature 1201, is considered in the determination ofwhether the engine is idling. In another embodiment, no measurements aretaken if the engine has not been running for at least a given length oftime. In yet another embodiment, no correction is made for the length oftime for which the engine has been running.

Turning now to the Fuel type module 1204, this module makes adjustmentsto the engine speed threshold according to fuel type.

We next consider the engine size module 1205. This module adjusts theengine speed threshold according to the engine size of the vehicle.

Turning now to the Clutch check module 1206, this module detects if thevehicle is being held on a hill on the clutch.

As part of the detection of the Engine Load Reporting Strategy, theengine load reporting strategy module 1207 (idling check) takes thevalues of the engine speed 503, vehicle speed 405 and engine load 504 todetermine whether the engine is idling and then checks whether theengine load reported is less than a threshold. If it is less than agiven threshold, it is determined that, since the engine load reportedis comparatively small, the value reported must be a percentage ofmaximum torque. Alternatively, if the engine load reported is above thethreshold, then the value reported is the percentage of power at thegiven engine speed. An indicator as to which strategy has been detectedis then passed on to the persistency check and latch module 1208. Thepersistency check module ensures that the strategy is only recorded ascorrect if the indicator has been set to the level for a given timethreshold. If this persistency check is passed, then the latch circuitensures that a strategy indicator is continuously provided to an output1209, even after the period of idling has ended.

The fuel type has been mentioned and referred to several times as partof this process. In particular, the fuel type, i.e. whether it is dieselor petrol, is of critical importance in the determination of thresholdsused in determining qualifying periods. An example of this is the enginespeed threshold used in determining the engine load reporting strategy.

According to an embodiment of the invention, there is provided amechanism for determining whether the vehicle uses diesel or petrol.This mechanism exploits certain differences in the operation of dieseland petrol engines. Amongst these differences are the mechanism forcontrol of the engine load, temperature differences in the exhaustgases, differences in the on board diagnostic protocols used, thereporting of fuel status and differences in fuel pressure.

In a petrol engine, load control is achieved by “throttling” the engine,which entails restricting airflow and hence reducing the availableoxygen to burn. Petrol engines are almost always constrained to run at astoichiometric fuel ratio. Diesel engines operate under normalconditions without a throttle in the intake manifold. Variation in theload on a diesel engine is achieved by careful fuel quantity deliveryalone.

In some vehicles the manifold pressure is reported, which allows astraightforward check to see if the engine is throttled. If the engineis running and a significant vacuum occurs, this is indicative that theengine is a petrol engine. A typical value detected is in the region of50 KPa below atmospheric pressure, but the person skilled in the artwill recognise that other suitable values may be used and the inventionis not limited to any particular threshold of manifold pressure. Whenthe vacuum condition is observed for a significant period, then thevehicle is recognised as having a petrol engine, otherwise, it isrecorded as using diesel.

In other vehicles the manifold pressure is not reported. In these cases,the air flow rate may be checked. If the air flow is less than apredetermined fraction of the engine size, this is an indication thatthe engine is being throttled, which, as stated, identifies the engineas running on petrol. A typical fraction of the engine size is1/300^(th), but the person skilled in the art will appreciate thatalternative values for this fraction may be used and the invention isnot limited to any given predetermined fraction.

Another mechanism which may be used to identify the fuel type is exhaustgas temperature. The temperature of the exhaust gases is much higher ina petrol engine than a diesel one. This fact can be used to provide analternative mechanism for the detection of fuel type. In an embodimentof the invention, the exhaust gas temperature is compared with at leastone threshold. In further embodiments, upper and lower thresholds areused.

Another indicator of the fuel type is the protocol used by the on boarddiagnostics system. One such protocol is the J1939 protocol, which isused exclusively by Heavy Goods Vehicles (HGV's). HGV's are usuallyfuelled by diesel and therefore detection of the J1939 protocol will beindicative that the vehicle is powered by a diesel engine. In anembodiment of the invention, an OBD protocol sniffer is used to identifythe protocol used. The protocol type is represented by an enumeratedstate and if the enumerated state corresponds with a value representingthe J1939 protocol we may assume it is an HGV vehicle. However, someHGV's are fuelled by Biogas, so use of the J1939 protocol is notconclusive proof of the use of diesel fuel. Since biogas has similarexhaust gas temperatures to petrol engines, a diesel is only reported bythe protocol detection system if the exhaust temperature is also that ofa diesel.

A further significant difference in the operation of diesel and petrolengines is the pressure at which the fuel is supplied. This value issignificantly higher in diesel engines and this fact may be used torecognise a diesel fuelled vehicle. In an embodiment of the invention,the common rail fuel pressure is compared with a predetermined thresholdin order to identify a diesel engine.

In addition, petrol engines can be identified by reference to one of thestandard OBD parameter identifiers (PIDs), namely PID 03, the fuelstatus type. A request can be made to the OBD as to the fuel status,which can be cold start, closed loop or component protection. Whilepetrol engines use this status PID, diesels do not. Therefore, in anembodiment of the invention, a request is made to the OBD for PID 03. Ifthere is a response, this indicates that the engine is fuelled bypetrol. If the request times out, this is indicative of a diesel engine.

Various embodiments of the invention are possible, which use the abovefuel type detection methods. The person skilled in the art willappreciate that any individual method or combination of methods may beused to determine the fuel type of the vehicle and the invention is notlimited to any one or any one combination of methods. In an embodimentof the invention, all of the methods are used in combination. However,the different indicators are not all equally conclusive of fuel type.The fuel pressure is not completely conclusive, as there is thepossibility of a high fuel pressure petrol engine. The use of the fuelstatus, presence of throttling and high exhaust gas temperatures are allstrong indicators of a petrol engine.

Setting out the fuel type detection mechanism in more detail we refer toFIG. 13.

FIG. 13 illustrates a fuel type detection module according to anembodiment of the invention. There is provided a Pressure And Flow RateModule 1301, Protocol Recognition Module 1302, an Exhaust GasTemperature Module 1303, a Fuel Pressure Module 1304, a latch circuit1305 and a manual override 1306. The Fuel Type Detection Module isprovided with six inputs; Manifold Absolute Pressure 1307, ManifoldAbsolute Pressure Validity Indicator 1308, Engine speed 503, Air flowrate 1309, Air flow validity indicator 1310 and Engine size 1311, theProtocol recognition module has one input, the Protocol Type Input 1312.The exhaust gas temperature module has two inputs, Exhaust GasTemperature 1313, and Exhaust Gas Temperature Valid 1314. The fuelpressure module has two inputs, Fuel Pressure 1316, and Fuel RailPressure Valid 1317. The manual override module has one input: ManualOverride 1318.

The Protocol recognition module 1302 takes the value of the enumeratedstate from the OBD protocol sniffer and checks it against J1939enumerated states held in module 1302. If the Exhaust Gas TemperatureModule also indicates a diesel, then the vehicle is recorded as beingfueled by diesel. If any of the Pressure And Flow Rate Module, ExhaustGas Temperature Module or Fuel Status Type Valid indicators indicatethat the vehicle uses petrol, then a petrol fuel type is recorded.

In an alternative embodiment of the Fuel Type Detector, the logicrepresented by the combination of AND gates 1319, 1320, OR gates 1321,1322 and NOT gates 1323, 1324 and 1325, is replaced by a “trust level”system, wherein a percentage or other numerical indicator is used torecord a confidence level that the vehicle is petrol or diesel whichreflects the degree of certainty in the respective test. A higher valuefor the trust level will for example be assigned to the throttling testthan for the fuel pressure. The trust levels are then summed and theresult is compared with a threshold to determine if the vehicle ispetrol or diesel fuelled.

All the factors contributing to the fuel consumption have now been setout.

The final stage of the process is the calculation of fuel consumption.In order to carry out a fuel calculation as accurately as possible, thepower required to keep the engine running must also be accounted for,including the power supplied to ancillary devices, and transmissioninefficiencies must also be taken into account. This is largelyconventional and will not be discussed further.

There are other factors which must be taken into account however, suchas braking events, for example. On a simple level, acceleration duringsuch braking events will be negative which might prevent generation ofaccurate values. This is of course not the case if the vehicle hasregenerative braking.

Once a total power figure, including ancillaries, has been calculated,this total power figure is divided by the transmission efficiency toproduce a figure for total engine power. The total engine power is thendivided by the engine efficiency and the calorific value of the fuel toproduce a value for fuel consumption. In an embodiment of the invention,an additional check is provided, whereby a user input maximum powerfigure is used as a maximum engine power. The lesser of the calculatedmaximum power and the user input figure is used in the fuel calculation.

Thus a value for fuel consumption may be calculated, for example, foreach period of an OBD cycle or other periods. For example fuelconsumption may be calculated as a continuous process during vehicleoperation. Any such fuel consumption calculations will be based oncharacteristics of a vehicle, characteristics of a driver, such asdriver behaviour, and characteristics of a journey. The fuel consumptionis therefore very specific to the vehicle, the driver, and the roadconditions and provides a degree of accuracy not achieved before.Several methods are provided herein to calculate a fuel consumption sothat if one of the methods cannot provide a value an alternative canreplace or supplement such a value. For example, in an embodiment of theinvention, upper and lower limits on fuel consumption may be establishedusing the method based on estimation of total power usage (i.e. usingequations 1 to 5). The upper and lower limits correspond to upper andlower estimates of vehicle mass, using the method illustrated in FIG. 8.The air flow method, the steps of which are illustrated in FIG. 1, maybe used as the principal mechanism for fuel consumption estimation, withthe upper and lower limits provided by the total power method providingappropriate “ceilings” and “floor” on fuel consumption estimation.Alternative combinations of the two methods may be used as appropriate.

FIGS. 14 and 15 illustrate embodiments of the system described above.Some exemplary findings from the system are given as follows.

Exemplary Findings.

During development we have relied on a variety of methods. In particularwe have simulated power at the crank. Applying a transmission efficiencyfactor of 0.95/0.9 (light/heavy) gives apparent power at the crank. Toobtain fuel we use the calorific value of the given fuel. The currentmodel is designed for diesel only. The internal combustion engineefficiency is given as 0.33/0.35 (light/heavy).

The variable subsystem as it stands to date. This is currently anengineering release.

Engine size must not exceed 1999 cc otherwise the model will load HGVsettings. etm_model_variables, vehicle mass, frontal A and coefficientof drag are calibrations in the model.

This model has been designed for use with a Mercedes Actros. The Actrosneeds to work without any requests being broadcast over OBD. This beingsaid, the model is designed to use only GPS speed delivered at 1 Hz froma TomTom link box via Bluetooth. The variables which must be configuredfor specific vehicles are as follows:

-   -   Vehicle mass (kg)    -   Frontal Area (m̂2)    -   Coefficient of aero drag (Cd)    -   Coefficient of rolling resistance (f)    -   Peak power (kW)

In order to utilize this model, the following conditions must be met:

-   -   con_ign_on==True    -   con_eng_speed_valid==False    -   con_veh_speed_valid==False

With the 3 variables set as stated above, etm_gps_vss_valid is set true.The Actros needs to be identified during sniffing and then once OBDrequests are halted the given conditions are met. For an MAN HGV, whereengine speed is valid but VSS is not, the AOP model uses GPS for speed,but the autocal model is still used for fuelling.

In order to display fuel the TomTom Link box must observe the following:

-   -   An active OBD connection (not the NVM value but the current        sniff connection)    -   con_ign_on==true    -   A Bluetooth connection with the micro.

To achieve this for the Actros, con_ign_on is set using ‘vbatt’. AnActros OBD session should not be live the calibration:‘appc_gps_overide_snif_rp’ should be set true when an Actros is detectedand the OBD communication is terminated. Relevant code found inmsg_tomtom_per_trip.c:

-   -   if(appc_gps_overide_snif_rp==TRUE)    -   {*p_dest++=8;}

For debugging this model on the bench, it is necessary to invalidateengine speed and vehicle speed, also ‘app_gps_speed’ is populated withthe value which would normally exist as con_veh_speed. This is achievedby setting the ‘appc_gps_overide_obd’ TRUE. This value should always beFALSE at build time, to ensure the model performs as intended!

Debugging:

appc_gps_overide_snif_rp==FALSE (This value should not affect us as itis just for TomTom's msg)appc_gps_overide_obd==TRUE

Release:

appc_gps_overide_snif_rp==TRUE (This value should not affect us as it isjust for TomTom's msg)appc_gps_overide_obd==FALSE

As already stated, this engineering release is Actros focused, onceengine size is configured correctly and it exceeds 2 litres, the modelwill pick expected values for an Actros and populate the variableslisted above. The model currently looks like this:

Model verification was conducted. Vehicle speed profile was recorded andchopped into 1 Hz interval (as found on a GPS reporting TomTom linkbox). The model has been verified by measuring expected fuel efficiencyof a 1994 Citroen ZX. An expected result for this vehicle is givenbelow:

-   -   Citroen ZX 1.9, expected=52 mpg, model result=53.02 mpg    -   Vehicle mass (kg)=1200 kg    -   Frontal Area (m̂2)=2.13 m̂2    -   Coefficient of aero drag (Cd)=0.33    -   Coefficient of rolling resistance (0=0.02, (with fudge factor        set to 0.5)

The model was then run using data for a Mercedes Sprinter, results givenbelow:

-   -   Mercedes Sprinter 2.2, expected=32.7 mpg, model result=33.0 mpg    -   Vehicle mass (kg)=1900 kg    -   Frontal Area (m̂2)=3.25 m̂2    -   Coefficient of aero drag (Cd)=0.38    -   Coefficient of rolling resistance (0=0.02, (with fudge factor        set to 0.5)

The model was then run using data from a number of HGV tests to ensurefuel accuracy is within acceptable limits for use on a Mercedes Actros,results given below: Note that the coefficient of rolling resistanceremains constant, this is intentional for all vehicle modelling.

-   -   Scania R430, expected=8.75 mpg, model result=8.32 mpg    -   Vehicle mass (kg)=23500 kg    -   Frontal Area (m̂2)=10.0 m̂2    -   Coefficient of aero drag (Cd)=0.42    -   Coefficient of rolling resistance (0=0.007, (with fudge factor        set to 0.5)    -   Iveco Stralis rigid 6×2 tag axle, expected=8.77 mpg, model        result=6.42 mpg    -   Vehicle mass (kg)=21000 kg    -   Frontal Area (m̂2)=10.0 m̂2    -   Coefficient of aero drag (Cd)=0.42    -   Coefficient of rolling resistance (0=0.007, (with fudge factor        set to 0.5)

This inaccurate result is rich due to over predicting power required foracceleration. The coca-cola cycle comprises many harsh transients.Simulating the truck empty at 10,000 kg—fuel economy is 10.99 mpg.

As an exercise, a steady state cruise simulation was conducted at 90kph. It was found that a 10,000 kg lorry uses a simulated 3.63 g/s ofdiesel. An identically sized 21,000 kg lorry produces 4.49 g/s, 19% morefuel as a result of rolling friction alone. The invention is not limitedto the features disclosed herein.

1. A method comprising: detecting signals from an on board diagnostics(OBD) port of a vehicle that is connected to an engine control unitwithin the vehicle, while the vehicle is moving along a surface;obtaining, from the detected signals, operating parameters of thevehicle including a power parameter and a speed parameter; andestimating effective frontal area of the vehicle based on the powerparameter and the speed parameter.
 2. The method of claim 1, whereinestimating the effective frontal area includes determining at least oneperiod of time during which the vehicle is moving along the surface at aconstant speed; and for one or more of the detected signals obtainedduring the at least one period of time, estimating the effective frontalarea by: determining a total power of an engine of the vehicle,determining a rolling resistance power to overcome a rolling resistanceof the vehicle at the constant speed, determining a power loss valueattributable to the effective frontal area by subtracting the determinedrolling resistance power from the determined total power, and utilizingthe power loss value to determine the effective frontal area.
 3. Themethod of claim 2, wherein determining the at least one period of timeincludes determining the at least one period based on the speedparameter, the speed parameter including one or more of vehicle speed,vehicle acceleration, engine speed and engine load.
 4. The method ofclaim 3, wherein determining the at least one period includes comparingthe one or more of vehicle speed, vehicle acceleration, engine speed andengine load with one or more predetermined reference values.
 5. Themethod of claim 2, wherein determining the rolling resistance includesdetermining the rolling resistance based on a gradient of the surfacealong which the vehicle is moving.
 6. The method of claim 2, whereindetermining the power loss value includes: determining an expected powerat a crank of the vehicle during periods of steady state and at aconstant speed without aerodynamic resistance; determining an actualamount of power applied to the crank based on engine load valuesprovided by the one or more detected signals; and determining the powerloss value based on a difference between the actual amount of powerapplied to the crank and the expected power at the crank.
 7. The methodof claim 1, wherein estimating the effective frontal area includesestimating aerodynamic resistance of the vehicle, and estimating thefrontal area based on the estimated aerodynamic resistance, the speedparameter and a coefficient of drag for the vehicle.
 8. The method ofclaim 1, further comprising estimating total current power for thevehicle during a period in which the vehicle is travelling at a constantspeed, wherein estimating the effective frontal area includes using theestimated total current power.
 9. The method of claim 8, whereinestimating the total current power includes using an engine loadparameter obtained from the detected signals.
 10. The method of claim 8,wherein estimating the total current power includes estimating the totalcurrent power based on expected transmission losses.
 11. The method ofclaim 10, wherein estimating the total current power based on expectedtransmission losses includes subtraction and/or multiplication of anobtained power value by one or more empirical power factors.
 12. Themethod of claim 1, further comprising estimating total current power forthe vehicle during each of a plurality of periods in which the vehicleis travelling at a constant speed, and determining a moving or weightedaverage of the total current power over the plurality of periods,wherein estimating the effective frontal area includes using the movingor weighted average of the total current power.
 13. The method of claim12, wherein determining the moving or weighted average of the totalcurrent power includes, for each of the plurality of periods:calculating an average value of the total current power over the period;and at an end of each period, calculating a weighted average between thecalculated average value and a value obtained from previous periods. 14.An apparatus comprising: a first circuit module configured and arrangedto couple to an on board diagnostics (OBD) port of a vehicle that isconnected to an engine control unit within the vehicle, and to detectsignals from the OBD port while the vehicle is moving along a surface;and a second circuit module configured and arranged to estimate frontalarea of the vehicle by: obtaining, from the detected signals, operatingparameters of the vehicle including a power parameter and a speedparameter; and estimating effective frontal area of the vehicle based onthe power parameter and the speed parameter.
 15. The apparatus of claim14, wherein the second circuit module is configured and arranged toestimate the effective frontal area by: determining at least one periodof time during which the vehicle is moving along the surface at aconstant speed; and for one or more of the detected signals obtainedduring the at least one period of time, estimating the effective frontalarea by: determining a total power of an engine of the vehicle,determining a rolling resistance power to overcome a rolling resistanceof the vehicle at the constant speed, determining a power loss valueattributable to the effective frontal area by subtracting the determinedrolling resistance power from the determined total power, and utilizingthe power loss value to determine the effective frontal area.
 16. Theapparatus of claim 15, wherein the second circuit module is configuredand arranged to determine the at least one period of time based on thespeed parameter, the speed parameter including one or more of vehiclespeed, vehicle acceleration, engine speed and engine load.
 17. Theapparatus of claim 15, wherein the second circuit module is configuredand arranged to determine the power loss value by: determining anexpected power at a crank of the vehicle during periods of steady stateand at a constant speed without aerodynamic resistance; determining anactual amount of power applied to the crank based on engine load valuesprovided by the one or more detected signals; and determining the powerloss value based on a difference between the actual amount of powerapplied to the crank and the expected power at the crank.
 18. Theapparatus of claim 15, wherein the second circuit module is configuredand arranged to determine the power loss value by further subtractingestimated transmission losses in the vehicle, and to determine theeffective frontal area by utilizing the power loss value to estimateaerodynamic resistance of the vehicle and to determine the effectivefrontal area based on the estimated aerodynamic resistance.
 19. Theapparatus of claim 14, wherein the second circuit module is configuredand arranged to: estimate total current power for the vehicle using anengine load parameter obtained from the detected signals during a periodin which the vehicle is travelling at a constant speed, and estimate theeffective frontal area using the estimated total current power.
 20. Theapparatus of claim 14, wherein the second circuit module is configuredand arranged to estimate total current power for the vehicle during eachof a plurality of periods in which the vehicle is travelling at aconstant speed, determine a moving or weighted average of the totalcurrent power over the plurality of periods, and estimate the effectivefrontal area by using the moving or weighted average of the totalcurrent power.